Cemented carbides composed mainly of WC, and sintered alloys such as cermets composed mainly of Ti (Ti-based cermets) are currently widely used as members requiring wear resistance and sliding properties, as well as fracture resistance, such as cutting tools, wear-resistant members, and sliding members. Developments of novel materials for improving performance of these sintered alloys are continued, and improvements of the characteristics of the cermets are also tried.
For example, patent document 1 discloses that wear resistance, fracture resistance, and thermal shock resistance are improved in the following method. That is, the concentration of a binder phase (iron-group metal) in the surface portion of a nitrogen-containing TiC-based cermet is decreased than that in the interior thereof so as to increase the ratio of a hard phase in the surface portion, thereby allowing a compression residual stress of 30 kgf/mm2 or more to remain in the surface portion of the sintered body. Patent document 2 discloses that WC particles as primary crystals of WC-based cemented carbide have a compression residual stress of 120 kgf/mm2 or more, whereby the WC-based cemented carbide has high strength and therefore exhibits excellent fracture resistance.
Patent document 1: Japanese Unexamined Patent Publication No. 05-9646
Patent document 2: Japanese Unexamined Patent Publication No. 06-17182